1. Field of Invention
This invention concerns a method for extraction and removal of at least 70% of cholesterol from liquid egg yolk with simultaneous production of unbound or free cholesterol as a by-product. In particular, this invention concerns (a) a production of decreased cholesterol liquid egg yolk by removal of cholesterol from the untreated liquid egg yolk into a vegetable extraction oil using ultra high pressure homogenization; (b) removal of cholesterol from the extraction oil by suitable methods to make the oil recyclable; and (c) the isolation of cholesterol from the oil as the by-product of the cholesterol extraction from liquid.
2. Related Disclosures
A growing consumer demand for reduced cholesterol products led to development of many methods for extraction of cholesterol from the liquid or dry egg yolk and its products. The primary disadvantages connected with these methods are the need for chemical or mechanical pretreatment of the liquid egg yolk. These pretreatments tend to change the taste, appearance and/or the texture of the egg yolk. Moreover, many of these methods use solvents which may present health risk or are so harsh that the restoration of the egg texture is impossible. The use of such decholesterolized egg product is greatly limited and commercially unsound.
Over years, many of these methods were patented. For example, the U.S. Pat. No. 3,958,034 describes a fractionation of the egg yolk material by centrifugation into cholesterol, fat, and protein. The described ultracentrifugation method is lengthy and costly. U.S. Pat. No. 3,563,765 concerns the process for obtaining low cholesterol dry egg yolk with extraction into hexane, an organic solvent undesirable to be used in processing the food for human consumption.
The vegetable oil extraction of cholesterol has been described in the U.S. Pat. No. 4,103,040 and in its predecessor, the U.S. Pat. No. 3,717,474. The described extraction is lengthy and is achieved with large volumes of the nonrecyclable oil which makes it neither practical nor economical. Four to twenty-five times more of fresh oil than yolk is needed for each extraction, which is twice to twelve times the cost of the yolk. The required quantities of oil needed for each extraction result in an unacceptable increase in production cost.
U.S. Pat. No. 4,234,619 concerns decholesterolized and defatted egg powder and method of producing such egg powder by extraction of cholesterol into dimethyl ether. Again, this method involves the use of unhealthy and hazardous solvent for use with foodstuff for human consumption. U.S. Pat. No. 4,333,959 concerns a process of reducing the amounts of cholesterol in egg yolk vegetable oil dispersion by centrifugation. All above-named processes are either unhealthy or highly uneconomical.
Thus, it would be highly desirable to have available method for cholesterol extraction from the egg yolk which method would avoid a need for pretreatment of eggs or the use of harmful solvents and which would, at the same time, also be industrially feasible and economical.
Vegetable oil extraction processes, as described above, were shown to be able to achieve substantial removal of cholesterol. However, the amount of the fresh oil needed for cholesterol extraction, usually from four to 25 (weight/weight) times more than the egg yolk makes such processes impractical and uneconomical because after the extraction, such oil must be discarded. Even when as low amount of the oil, i.e., only two times more of the fresh oil than egg yolk is used, if such oil is not recyclable, the waste of the oil on such a large scale is not economically feasible.
Thus, it would be of great advantage to have a procedure which would allow the removal of substantial amount of cholesterol from the egg yolk into the oil and subsequent removal of cholesterol from the oil making such oil suitable for reuse or recycling for further cholesterol extraction from the egg yolk.
Methods for removal of odors, a deodorization of oxidized fish oils have been described in U.S. Pat. Nos. 4,804,555 and 4,996,076. These patent describe a technique known as a steam stripping. The steam stripping removes almost all non-esterified cholesterol from fish, dairy oils, and fats.
The steam stripping removal of cholesterol from the egg yolk directly has not been hitherto described and is probably not feasible without making the egg yolk-oil emulsion and even then, without special treatment, the egg yolk would coagulate and clog the steam stripping apparatus making the process highly impractical. Moreover, even if such methods were available, because of the large amount of cholesterol contained in the egg yolk, the removal of such large amount of cholesterol as a waste would be uneconomical and rather burdensome.
On the other hand, production or synthesis of cholesterol for its many industrial uses is very costly with production cost for one pound of non-purified cholesterol running around $28-$30. While a production of lecithin is described in U.S. Pat. No. 4,822,926 and the extraction of oil from egg yolk is disclosed in U.S. Pat. No. 4,219,585, the production of cholesterol from the egg yolk wherein the egg yolk would be preserved and utilized is not known.
It would thus be extremely useful to utilize the method for removal of unbound cholesterol from the liquid egg yolk for simultaneous production of cholesterol as the by-product.
It is, therefore, a primary object of this invention to provide a method for substantial (70%-98%) removal of cholesterol from the egg yolk by ultra high pressure homogenization extraction into a vegetable extraction oil, combined with the steam stripping removal of cholesterol from the oil laden with cholesterol removed from the egg yolk, and with the subsequent separation, isolation, and purification of cholesterol for industrial use.
All cited references and patents are hereby incorporated by reference in their entirety.